The invention relates to an adjustment process of an electronic trip device comprising an analog channel whose input is connected to means for measuring current, the channel comprising at least a measuring resistance connected to the means for measuring current and at least a first operational amplifier connected to the terminals of the measuring resistance.
Conventional electronic trip devices comprise a certain number of adjusting resistances designed, at the end of manufacture, to adjust the characteristics of the trip device with a preset precision. Generally an adjusting potentiometer is connected in series with a resistance to form the adjusting resistance. This manual adjustment process is long and costly. It has also been proposed to use networks of resistances connected in parallel, each resistance of the network being connected in series with a fuse component. Selective blowing of one or more of these fuse components enables the value of the resistance equivalent to the network to be adjusted accurately. In some microprocessor-based trip devices an electrically alterable read-only memory (EAROM) is used to store a correction factor to be applied to the measured values.
Conventional adjustment processes are long and costly. The object of the invention is to provide an automatic adjustment process designed to maintain the characteristics of the trip device within preset limits.